isDisable is not working as expected?

[Sagar535]

isDisabled: function (date, mode) {
          console.log('checking if the date is disabled');
          const day = date.getDate();
          if (day == 29 || day == 30 || day == 31) {
              return true;
          }
          return false;
      },

I'm trying to disable the date that has day greater than 28 but it is not working...?

[lubber-de]

Your code is working totally fine, at least when using https://github.com/fomantic/Fomantic-UI/ where the calendar has been merged into and gets further maintenance. See https://jsfiddle.net/cuf5qwy0/